The present invention relates to a combinatorial X-ray diffraction apparatus, and, more specifically, to an X-ray diffraction apparatus for combinatorial evaluation of epitaxial thin film, which apparatus can simultaneously measure, through X-ray diffraction, samples in one column, among a plurality of samples disposed in a matrix pattern.
When a new functional material is produced through mixing various elements (elements/molecules), determining an optimal composition and mixing proportions is difficult. In particular, when the number of component elements and the molecular weight of a material to be produced are increased, a conventional approach; i.e., a process of producing different materials on a material-by-material basis while gradually changing the production conditions and investigating the properties of the materials on a material-by-material basis, requires an astronomical amount of time and is therefore difficult to employ.
In order to solve the above-described problem, an approach called combinatorial chemistry has been proposed. Under this approach, a region in which production of a target material is highly probable is screened systematically. This approach drastically improves synthesis efficiency of new organic substances such as polypeptides.
FIG. 1 illustrates the principle of combinatorial chemistry. A method called parallel synthesis will be described briefly.
First, as shown in FIG. 1(a), a large number of reaction chambers are prepared. Component materials are placed in the reaction chambers such that composition and mixing proportions vary in the row and column directions, respectively. Upon simultaneous reaction, as shown in FIG. 1(b), a large number of different materials resulting from systematical combination of different compositions and proportions are obtained concurrently. That is, when this approach is used, materials research can be performed quite efficiently as compared with the case in which a material corresponding to each different combination is produced through reaction. Further, since a large number of combinations can be tested under identical conditions, the production conditions can be made uniform among the different materials, which is extremely advantageous.
If this approach is applied to fabrication of thin film, it becomes possible to fabricate on a single substrate a thin film of a material in which the proportions of two elements are changed gradually. Specifically, three targets of, for example, ZnO, Co0.1Zn0.9O, and Fe0.1Zn0.9O are prepared, and deposition is performed while the amounts of deposition are controlled by use of a mask. Thus, thin films of FexCoyZn1xe2x88x92xxe2x88x92yO are formed on a single substrate such that the compositional proportions x and y vary among the thin films. Further, the above-described method enables production of a superlattice in which the stacking cycles of respective compounds are varied.
A secondary important point is efficient performance of evaluation which is performed for finding prospective combinations by use of the thus-formed thin films having different compositions and/or stacking cycles.
A very important step is to evaluate the crystalline structures and lattice constants of thin films which have been fabricated in the manner as described above and which have different compositions and/or stacking cycles. However, a conventional evaluation method performed by use of an X-ray diffraction apparatus premises that a material to be evaluated has a uniform structure in a region irradiated with an X-ray. Therefore, when the composition and structure of the material vary among narrow regions, radiation of an X-ray beam must be restricted such that the X-ray beam is radiated only to a region of uniform structure.
Further, in order to evaluate all the fabricated films, measurement must be repeated a large number of times, which requires a very long time. Therefore, even if thin films of different compositions can be efficiently fabricated concurrently, evaluating the fabricated films requires a long time. Therefore, overall efficiency is not high.
Therefore, an X-ray diffraction apparatus capable of quickly evaluating an object whose structure varies depending on position is demanded.
In view of the forgoing, an object of the present invention is to provide a combinatorial X-ray diffraction apparatus which can efficiently use X-rays from an X-ray source and which can quickly perform accurate measurement and evaluation of a large number of epitaxial thin films disposed at different positions.
To achieve the above object, the present invention provides the following:
[1] A combinatorial x-ray diffraction apparatus comprising: an X-ray source for radiating X-rays from a point-shaped focal point; a curved monochromator which spectrally reflects the X-rays radiated from the X-ray source; a slit disposed for restricting radiation of the reflected X-rays to a measurement area; a knife-edge slit disposed for selecting a desired portion of the X-rays having passed through the slit; a holder for holding a combinatorial epitaxial thin film to be irradiated with the X-rays restricted by the knife-edge slit; a two-dimensional detector for receiving diffraction X-rays reflected from the epitaxial thin film held by the holder; a goniometer having a xcfx89-axis shaft and a 2xcex8-axis shaft, the holder being mounted on the xcfx89-axis shaft, and the two-dimensional detector being mounted on the 2xcex8-axis shaft; a drive unit for moving the position at which the X-rays impinge the epitaxial thin film; an information processing apparatus for fetching output data from the two-dimensional detector and processing the data; and a display unit for displaying the result of processing performed in the information processing apparatus.
[2] A combinatorial X-ray diffraction apparatus comprising: an X-ray source for radiating X-rays from a line-shaped focal point; a curved monochromator which reflects the X-rays radiated from the X-ray source, while converting the X-rays to monochromic rays; a slit disposed for restricting radiation of the reflected X-rays to a measurement area; a knife-edge slit disposed for selecting a desired portion of the X-rays having passed through the slit; a holder for holding a combinatorial epitaxial thin film to be irradiated with the X-rays restricted by the knife-edge slit; a Soller slit which affects the X-rays having passed through the knife-edge slit; a two-dimensional detector for receiving diffraction X-rays reflected from the epitaxial thin film held by the holder; a goniometer having a xcfx89-axis shaft and a 2xcex8-axis shaft, the holder being mounted on the xcfx89-axis shaft, and the two-dimensional detector being mounted on the 2xcex8-axis shaft; a drive unit for moving the position at which the X-rays impinge the epitaxial thin film; an information processing apparatus for fetching output data from the two-dimensional detector and processing the data; and a display unit for displaying the result of processing performed in the information processing apparatus.
[3] A combinatorial X-ray diffraction apparatus as described in or [1] or [2] above, further characterized in that the combinatorial epitaxial thin film includes a plurality of epitaxial thin films disposed in a column direction.
[4] A combinatorial X-ray diffraction apparatus as described in any one of [1] to [3] above, further characterized in that the apparatus is set such that, among cells of a plurality of epitaxial thin films formed in a matrix pattern in accordance with a combinatorial method, at least two cells forming a cell column simultaneously satisfy diffraction conditions.
[5] A combinatorial X-ray diffraction apparatus as described in any one of [1] to [4] above, further characterized in that the two-dimensional detector is disposed such that the two-dimensional detector can receive simultaneously X-rays from at least two cells forming a cell column, among cells of a plurality of epitaxial thin films formed in a matrix pattern in accordance with a combinatorial method.
[6] A combinatorial X-ray diffraction apparatus as described in any one of [1] to [5] above, further characterized in that the apparatus is set such that, among cells of a plurality of epitaxial thin films formed in a matrix pattern in accordance with a combinatorial method, cell columns each including at least two cells sequentially satisfy diffraction conditions, and in that the two-dimensional detector is disposed such that the two-dimensional detector can receive diffraction X-rays diffracted at the cell columns sequentially.
[7] A combinatorial X-ray diffraction apparatus as described in any one of [1] to [6] above, further characterized in that the spatial distribution of X-ray intensity and the spatial distribution of sensitivity of the two-dimensional detector are normalized; and for each pixel or each block of pixels of diffracted X-rays collected two-dimensionally, X-ray intensity correction is performed according to the position thereof.
[8] A combinatorial X-ray diffraction apparatus as described in any one of [1] to [7] above, further characterized in that diffraction X-rays diffracted at a cell column including at least two cells, among cells of a plurality of epitaxial thin films formed in a matrix pattern in accordance with a combinatorial method, are received simultaneously by the two-dimensional detector; positions of each cell in a direction of diffraction angle xcex8 and in a direction perpendicular thereto are measured; and diffraction X-ray intensities of pixels of the two-dimensional detector corresponding to each cell of the epitaxial thin film are integrated in order to individually obtain the intensity of diffraction X-rays from each cell.
[9] A combinatorial X-ray diffraction apparatus as described in any one of [1] to [8] above, further characterized in that from diffraction X-rays diffracted at a cell column including at least two cells, among cells of a plurality of epitaxial thin films formed in a matrix pattern in accordance with a combinatorial method, the intensity of a diffraction X-ray from each cell is separated and related with angle information representing a diffraction angle xcex8, through movement of the epitaxial thin film on the goniometer and the movement of the two-dimensional detector, within a desired angle range.
[10] A combinatorial X-ray diffraction apparatus as described in [8] or [9] above, further characterized in that diffraction X-ray data obtained with respect to each cell are stored or displayed as they are or after being subjected to X-ray intensity correction or background elimination correction; or a peak intensity, a peak position, and half-value width are calculated from the data and are stored or displayed.
[11] A combinatorial X-ray diffraction apparatus as described in [10] above, further characterized in that, in addition to data processing, storage, or display, the diffraction X-ray data obtained with respect to each cell are subjected to additional data processing, storage, display, or data analysis which are performed under comparison with data with respect to each cell column or the combinatorial cell matrix.